This invention generally relates to ballasting systems and, more particularly, to ballasting systems for on-site sewage treatment and disposal systems.
Septic tanks with a leach or drain field are commonly used in areas without public sewer systems. A septic tank in a private waste disposal system receives household sewage, and separates the solid matter from effluent before the effluent is discharged. Bacteria in the septic tank decomposes or digests the sewage. The effluent is discharged to a drain or leach field, typically composed of underground perforated PVC piping or drainage tiles that distribute the liquid effluent into the earth, where additional bacterial action takes place.
Public health agencies and zoning codes for specific areas generally dictate the conditions for the installation of a septic system, as described above, and require a certain range of perc rates for the soil as well as a minimum depth below grade to groundwater (which provides a minimum thickness of unsaturated soil) in order to allow the leach field to operate in its intended manner.
Below grade leach field installations are generally not permitted in areas where the natural groundwater level is too high. While the specific requirements may vary from state to state, or by local jurisdictions and municipalities, generally, the seasonal high groundwater level must be at least three feet below grade in order to obtain a permit for installation of a below grade leach field.
One known solution to this problem is to install an elevated sand mound (a/k/a Wisconsin Mound”) above grade and place the leach field in the sand mound. A pump is then used to transfer effluent from the septic tank to the leach field. However, sand mounds are much more costly to install than below grade drain fields, and have an undesirable appearance.
An alternative to the sand mound system is a system, such as the one disclosed in U.S. Pat. Nos. 5,435,666 and 5,827,010, in which the separation distance is achieved by lowering the water table beneath the drain field. Such systems use air pressure to keep the water table down in order to achieve the required separation distance. The use of air pressure, however, also acts to force the system upward within the ground. Therefore, some form of ballast is necessary to maintain the system within the ground and inhibit it from migrating upwardly within the ground. Ballast, such as fill, engineered steel assemblies, and/or concrete slabs having a length and width exceeding a length and width of the drain field surface, has been used and is generally effective. However, the use of fill is prohibited in some areas, such as flood plains, and the use of steel as ballast is not optimal because steel tends to degrade over time and generally requires cathodic protection for corrosion control. Concrete slabs tend to be a relatively expensive ballast alternative. Additionally, concrete slabs are required to be broken up with a jackhammer or other such machine to be removed and cannot be easily disassembled and reused.
It is therefore desirable to provide a ballasting system which does not require fill, does not use steel, and/or does not require large, non-reusable concrete slabs for such below grade drain fields.